氮合金化堆焊硬面合金组织与耐高温磨损性能

对马氏体不锈钢堆焊硬而合金进行了氮合金化,研究了其组织和耐高温磨损性能.结果表明,氮合金化马氏体不锈钢堆焊层显微组织主要为马氏体和铌、钛的复合碳氮化物;堆焊马氏体不锈钢硬面合金与碳钢的高温金属间磨损,为碳钢表面高温下形成的氧化皮,粘着于堆焊马氏体不锈钢硬面合金表面,导致堆焊马氏体不锈钢硬面合金产生磨粒磨损.氮合金化堆焊...     

铁基堆焊耐磨合金的研究现状

概述耐磨堆焊材料、方法的分类及堆焊层合金元素的性质和堆焊层中碳化物形成特点;对铁基堆焊耐磨合金的固溶强化、第二相强化(弥散强化和析出强化)、晶界强化、热处理和定向凝固等强化方法进行了论述。分析合金元素在堆焊层中的作用、磨料磨损的形貌以及铁基耐磨合金的耐磨机理。铁基堆焊具有成本低、品种多,且易于改变堆焊层强度、韧性、耐磨性、抗冲击性等优点。铁基堆焊耐磨合金是当前研究的重要方向之一,应用前景广阔。     

Comparative evaluation of the abrasive slurry wear behavior of alloy surfaces produced by a Plasma Transferred Arc hardfacing process

Abrasive slurry wear is generally defined as a mechanical interaction in which the material becomes lost in a surface that is in contact with moving particles, such as laden liquid. Slurry wear abrasion occurs in extruders, slurry pumps, and pipes that carry the slurry of minerals and ores in mineral processing industries. The life of the components used under slurry abrasion conditions is governed by the process parameters, the properties of the abrasive particles in the slurry, and the material properties. This paper analyses in detail the effects of operating variables, such as abrasive particle size, slurry concentration, speed of rotation, and slurry bath temperature, on the abrasive slurry wear behavior of a iron based alloy (stainless steel), cobalt based alloy (stellite), and nickel based alloy (colmonoy) surfaces produced by a Plasma Transferred Arc (PTA) hardfacing process. Of the four variables considered in this investigation, it was found that the slurry concentration had a predominant effect on the wear rate of hardfaced surfaces compared to the other variables. Microstructural analyses of the worned surfaces were carried out using SEM. Both the experimental and mathematical investigations showed that the wear resistance of an iron based alloy was 4 times better than the base metal. Similarly, the cobalt based alloy exhibited a 3 times higher wear resistance while the nickel based alloy showed a 2 times higher wear resistance compared to the base metal (carbon steel).     

硼化物强化铁基堆焊合金显微组织与耐磨性

为了提高在严峻工况条件下工作的机械零件的耐磨性,采用等离子弧堆焊技术,制备硼化物强化铁基堆焊合金。借助OM,SEM和XRD等分析手段对合金组织和硼化物相形貌进行分析,并与未加入硼的Fe-Cr-C的堆焊合金进行对比。结果表明:堆焊合金中加入w(B)4.5%可改变基体的组织组成及硼化物的数量和分布形态,从而改善耐磨性。硼化物由大量菊花状M23(C,B)6和少量块状M7(C,B)3相组成,BC4与Cr2B的数量较少。耐磨粒磨损试验结果表明:堆焊合金的耐磨性随着硼含量的增加而先增大后下降,加入w(B)4.5%的堆焊层中形成的大量高硬度硼化物分布在具有较高强韧性的马氏体和奥氏体基体上,使其具有最佳的耐磨性,其磨损量仅为未加入硼时的1/6。     

AZ31镁合金表面强流脉冲电子束铝合金化研究

利用强流脉冲电子束对AZ31镁合金表面进行快速铝合金化,分析了表面合金化层的显微结构,测量了铝合金化前后,AZ31镁合金的腐蚀性能与耐磨性能.结果表明,经电子束轰击后表层出现了典型的熔坑形貌;耐磨性能测试表明,加速电压为27 kV,脉冲5次的试样比原始试样的相对耐磨性提高6倍,同时合金化也提高了在5%的NaCl溶液中的耐腐蚀性能.     

Effect of Al on High-Temperature Oxidation of Cr–W Alloys

The effect of Al on the high temperature oxidation behavior of Cr–10 wt.%W alloy was investigated using a cyclical oxidation test at 1,000 °C in dry air. First, Al was added into the Cr–W alloy as an alloying element up to 8 weight percent. Although alloying with Al reduced the spalling, it did not eliminate it. Secondly, Al was applied to the surface using an aluminizing process. Forming an Al–Cr layer on the Cr–W alloy reduced oxidation rate significantly and eliminated spalling completely.     

2090Ce铝锂合金的焊缝热裂纹敏感性及接头力学性能

采用焊缝合金化手段，通过设计新型焊丝向焊缝中添加Ｌｉ、Ｚｒ和Ｃｅ等合金化元素，研究了２０９０Ｃｅ稀土铝锂合金焊缝金属的热裂纹敏感性；探讨了合金元素对接头力学性能的影响及作用规律；进而研究了适用于焊接２０９０Ｃｅ合金的焊丝合金成分。试验结果表明，向焊缝金属中添加适量的合金元素Ｌｉ、Ｚｒ和Ｃｅ，能够细化晶粒；增加焊缝中的共晶数量并改善其分布形态，从而有助于降低焊缝金属的热裂纹敏感性。另外，适量的Ｌｉ、Ｚｒ和Ｃｅ等合金元素还能够在不降低接头塑性的同时，明显改善接头的强度；但Ｌｉ和Ｃｅ含量过多则会对接头性能，特别是塑性造成损害。所设计的焊丝材料能够适用于焊接２０９０Ｃｅ稀土铝锂合金。     

Microstructure and wear property of hardfacing alloy with nitrogen strengthening

The nitrogen-alloying hardfacing alloy of the martensitic stainless steel was deposited on a low carbon steel substrate using hardfacing flux-cored wire. Microstructure and surface hardness of hardfacing alloy were investigated and measured by optical microscope and microhardness tester. Carbonitrides of the hardfacing alloy were observed by electron probe. The wear behaviour of the hardfacing alloy was studied using the belt abrasion test apparatus and the worn surface was analyzed by scanning electron microscopy. The results showed that carbonitride particles in the hardfacing alloy are complex MX (M:alloy elements; X:C, N) precipitate with fine size. These carbonitride particles distributed homogeneously in the hardfacing alloy and had a good strengthening effect on the wear property. The wear property of the hardfacing alloy with nitrogen was better than the one without nitrogen.     

Some Physicochemical Phenomena Observed During Fabrication of Mg-C Cast Composites

Some effects acquired in composites processed under industrial conditions were presented. Glassy carbon particles (GCp) and short carbon fibers were applied in magnesium matrix composites fabricated by suspension casting. As the matrix magnesium alloys with Al and without Al but with Zn, Zr and rare earth elements (RE) were used. The main interest was focused on the behavior of the reinforcing components, depending on the magnesium alloying elements. The observation of the stirred suspensions during their industrial processing detected an effect of carbon components’ migration to the top of the crucible, suggesting segregation processes. Experiments with unmixed suspensions performed by way of remelting the composites with uniformly distributed reinforcement showed that the segregation effect depends on the magnesium matrix composition. In the case of the alloy with Al, two zones with (top) and without reinforcement can be formed. For the alloys with Zn, Zr, and RE, an additional zone of segregated carbon reinforcement can appear directly at the bottom of the crucible. The SEM/EDS examination also showed some differences in the influence of the magnesium matrix on the carbon reinforcement dependent on the applied alloying elements. The most destructive effect was detected for the Al-containing alloy and minor defects in GCp were formed when Gd with Nd were applied.     

Abrasive slurry wear behavior of stainless steel surface produced by plasma transferred arc hardfacing process

Abrasive slurry wear is generally defined as a mechanical interaction in which material is lost from a surface which is in contact with a moving particle-laden liquid. Slurry wear abrasion occurs in extruders, slurry pumps, and pipes carrying slurry of minerals and ores in mineral processing industries. The life of components used under slurry abrasion conditions is governed by the process parameters, properties of the abrasive particles in the slurry and the material properties. This paper analyzes in detail the effects of operating variables such as abrasive particle size, slurry concentration, speed of rotation and slurry bath temperature on the abrasive slurry wear behavior of a stainless steel surface produced by Plasma transferred arc (PTA) hardfacing process. Of the four variables considered in this investigation, it is found that the slurry concentration has a predominant effect on wear rate of hardfaced surfaces compared to other variables. Microstructural analyses of the worn surfaces were carried out using SEM. Both experimental and mathematical investigations show that the wear resistance of the PTA hardfaced stainless steel surface is four times better than that of the carbon steel substrate.     

钒对Fe-Cr-C耐磨堆焊层性能的影响

在Fe-Cr-C耐磨堆焊合金中加入钒,研究钒对Fe-Cr-C耐磨堆焊合金焊态和焊后热处理态性能的影响.采用埋弧堆焊方法在Q235低碳钢基体上制备了堆焊层,利用光学金相、SEM分析了堆焊合金的显微组织,并进行了硬度和磨料磨损试验.结果表明,焊后加热对Fe-Cr-C耐磨堆焊合金的硬度有较大影响.经过焊后加热,基体组织的硬度降低值都大于22%,降低值最大的是不含钒的Fe-Cr-C耐磨堆焊合金,达到37.7%.焊后加热对初生碳化物M7C3的硬度影响较小,其硬度降低值为1.4%～11.3%.含0.4%V可以有效的提高Fe-Cr-C耐磨堆焊合金高温热处理后的耐磨料磨损性能.以淬火态的45钢为标样,在经过900℃焊后热处理,含0.4%V的Fe-Cr-C耐磨堆焊合金相对耐磨性为1.9,而同样条件下不含钒的试样相对耐磨性只有1.3,两者相比,含0.4%V的合金相对耐磨性提高了46%.     

耐海水腐蚀铸铁的抗氧化性

探讨HD型铸铁（一种耐海水腐蚀低合金铸铁）高温氧化时能否形成类似保护膜的研究结果表明,HD铸铁在高温下形成的氧化膜与一般铸铁无本质区别,其抗氧化性主要与铸铁中Cr、Al、Si含量有关。     

Formation mechanism of titanium and niobium carbides in hardfacing alloy

The most effective carbide-forming elements titanium and niobium were added into hardfacing alloy.Formation and composition of carbides in the hardfacing alloy were investigated by means of optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD)and energy-dispersive spectrometer(EDS).Hardness and impact toughness of the hardfacing alloy were measured.The thermodynamics and formation mechanism of carbides were also discussed.It is found that the carbides consist of TiC and NbC which are able to form directly from welding pool during the welding process.The formation mechanism of carbides involves nucleation of TiC followed by epitaxial precipitation of NbC on the surface of TiC.The formation of titanium and niobium carbides can obviously refine the microstructure and deplete the carbon in the matrix.The micros tructure transforms to well-distributed carbides and a tough martensite matrix,contributing to a good combination of high hardness and high toughness in the hardfacing alloy.     

Ti6Al4V钛合金表面Zr-N合金化层的抗高温摩擦磨损性能

为了改善钛合金的高温耐磨性能,采用锆-氮离子共渗与异步渗(渗锆后再氮化处理)两种工艺技术分别在Ti6A14V钛合金表面制备致密的锆-氮合金化改性层,对比研究了合金化层的组织结构特征和高温摩擦磨损性能.结果表明,两种工艺制各的Zr-N合金层表面均由ZrN相组成,异步渗改性层的内层则包含较厚的Zr-Ti固溶体,两种等离子表面合金化层均使钛合金表面硬度显著提高.同样温度和处理时间条件下,异步渗合金化层的厚度约为锆-氮共渗合金化层厚度的6倍,且氮化物层也较厚,原因归于前者处理过程中Zr与Ti之间良好固溶特性的充分发挥及ZrN相的扩散障作用的有效抑制.300℃高温下球盘摩擦磨损试验结果表明,由于锆-氮共渗合金化层深度较小,因而改善钛合金基材耐磨性能的效果相对较低.锆-氮异步渗处理则使Ti6A14V钛合金耐磨性能显著提高,摩擦因数降低50％以上,比磨损率降低2个数量级,原因归于该类合金化层高的表面硬度、大的层深、良好的高温抗氧化性能及优异表面承载能力的有机匹配.     

The impact characteristics of Ti–6Al–4V plates hardfacing by laser alloying NiAl+ZrO2 powder

This investigation considers the alloying of NiAl powders, with 0, 10, 20, 30, and 40 wt.% of ZrO₂ added, by the CO₂ laser upon Ti–6Al–4V base metals. Trial experiments are performed to obtain the optimum thickness of the powder, 0.1 mm, and the transverse speed, 1 mm/s, upon which the hardfacing process was based. The microstructures of the alloying layers were analyzed by OM, X-ray spectroscopy and SEM/EDS. The mechanical properties of the alloying layers were analyzed by micro-hardness and impact tests. The results indicated that the microstructure of the hardfacing layer was finer and its micro-hardness was higher than those of the base material. During the hardfacing process, NiAl and ZrO₂ powder were dissolved in a molten pool, reacted with other elements, and new phases were then formed. Impact tests revealed that the absorption of the vibration increased as the ZrO₂ added.     

Predicting the dilution of plasma transferred arc hardfacing of stellite on carbon steel using response surface methodology

Control of dilution is important in hardfacing, where low dilution is typically desirable. At present, most fabrication industries use shielded metal are welding, gas metal arc welding, gas tungsten arc welding and submerged are welding processes for hardfacing purposes. In these processes, the percentage of the dilution level is higher, ranging between 10% and 30%. In Plasma Transferred Arc (PTA) hardfacing, a solidified metallurgical bond between the deposit and the substrate is obtained with minimum dilution (less than 10%). This paper highlights the application of response surface methodology to predict and optimize the percentage of the dilution of a cobalt-based hardfaced surface produced by the PTA process. Experiments were conducted based on a fully replicable five-factor, five-level central composite rotatable design and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was used to optimize the process parameters that yield the lowest percentage of dilution.     

钛合金圆环工件表面合金化及其滚动摩擦性能研究

采用等离子表面合金化技术在Ti6Al4V合金圆环工件表面制备Mo渗镀改性层,将其与未渗Mo处理的Ti6Al4V合金在模拟实际工况条件下进行油润滑的滚动摩擦对比试验,比较二者的磨损情况,并分析磨损机理。结果表明,Ti6Al4V合金表面进行渗Mo处理后,形成了均匀、致密且高硬度的Mo基改性层。Ti6Al4V合金表面渗Mo后,硬度由渗层到基体呈梯度分布。滚动摩擦试验表明,渗Mo处理后表面无减摩效果,但磨损量大大减小,耐磨性得到有效改进。通过对磨损形貌的分析可知,表面渗Mo处理后磨损机理主要以磨粒磨损为主,而基材是磨粒磨损和粘着磨损。     

NbC增强Fe-Cr-C耐磨堆焊合金组织与磨粒磨损性能

以H08A为焊芯,在Fe-Cr-C耐磨合金焊条药皮中加入NbC,对堆焊层组织及NbC对堆焊层硬度和耐磨性的影响进行了研究.结果表明,NbC增强Fe-Cr-C耐磨合金的宏观硬度和耐磨性都高于Fe-Cr-C合金,宏观硬度达到61.6 HRC,比Fe-Cr-C耐磨合金提高9.6%;相对耐磨性提高60%.NbC增强Fe-Cr-C耐磨合金中NbC硬质相断面呈不规则形状,分布于M7C3之间,或镶嵌在M7C3中,以菱形或多边形居多,NbC分布不均匀,有局部聚集的区域.与Fe-Cr-C耐磨合金的共晶碳化物比较,Fe-Cr-C-NbC合金的共晶碳化物要粗大,共晶碳化物的间距也较大.     

AZ31镁合金表面Al合金化层的制备与性能研究

为提高镁合金表面的耐蚀性,采用热喷涂技术在AZ31镁合金表面制备铝涂层,并利用脉冲钨极氩弧表面熔覆的方法进行表面重熔,获得富铝的合金化层,分析了合金化层的组织结构和性能。研究结果表明:在AZ31镁合金表面的铝合金化层中存在典型的树枝晶结构,含有金属间化合物Mg2Al3,Mg17Al12以及α-Mg和Al固溶体。显微硬度测试表明,铝合金化可使AZ31镁合金表面硬度由HV50左右提高到HV200左右。极化曲线测试表明,合金化层提高了镁合金表面的耐蚀性。     

Advanced methods of improving the quality and increasing the efficiency of welded structures

The process of hardfacing by plasma transferred arc (PTA) has been increasingly accepted in recent years. It has attractive features from the metallurgical point of view, as well as offering low distortion, little dilution, a homogenous structure, and refined coatings. Major innovations and optimized engineering component processing could be achieved if companies had access to a study of different processing parameters. However, owing to the scarcity of literature about the process, comparing it with other welding processes, which contains divergent information in some areas, demands a wider and more systematic study of the effect of the welding variables. This work is intended to contribute to this, and the main objective is to verify the effect of the process variables on the characteristics of a weld bead deposited by the PTA. Using a constant direct current, the influence of the sharpening angle was studied on a tungsten electrode, plasma gas flow, and torch nozzle constriction, using a cobalt-based alloy commercially known as Stellite 6 as the support material. The characteristics of the coating were evaluated in terms of their surface finish, dilution, wettability, and hardness. The results showed that the characteristics of the deposits were determined by the intensity of the current, followed by the nozzle constriction, and that the electrode sharpening angle did not influence the results.